But for more info Discord seems to show below the content of the meta description.

The meta description is currently just hardcoded text:

themes/CleanFS/templates/header.tpl
<meta name="description" content="Flyspray, a Bug Tracking System written in PHP." />

But what is appropriate to put into a dynamic generated meta-description tag? This question is not yet answered. Several solutions in my mind, but a solution should respect also the flyspray permissions.

The screenshot in this comment shows similiar behavior when trying to link a flyspray task as message on facebook. The automatic page grabbing done by facebook shows currently content of 'title-tag' and 'meta description'-tag.